Conventionally, a vehicle navigation apparatus detects, for the purpose of accurately displaying a current vehicle position, the current vehicle position and a white line on a road based on a captured image that captures a travel direction of a vehicle, and selects one of plural roads for matching the current vehicle position thereto based on a detection result of the white line if the current vehicle position is possibly matched to plural roads. A Japanese patent document JP-A-2005-345240 (US patent document 20080077322) discloses, for example, a navigation device configured to perform such operation.
Though the distance between intersections is an unambiguously-defined value, a travel locus of a vehicle may vary depending on a driving technique of a driver due to a lane change, a faltered driving, or due to a tolerance of a distance measurement (e.g., a change of the tire diameter) or the like, thereby leading to an un-matching between an actual travel distance and inter-intersection distance data on the map. Therefore, the current vehicle position has a predetermined tolerance range in a front and rear field and on a right and left side of the vehicle for matching control that matches the current vehicle position to a link within the tolerance range, for the purpose of accurately displaying the vehicle position when the vehicle makes a right or left turn at an intersection.
That is, as shown in FIG. 8, the matching link is searched within the tolerance range of the current vehicle position when the vehicle makes a left turn at the intersection, and the vehicle position is matched to a link (e.g., a link X in FIG. 8) that suitably matches with the current vehicle position within the tolerance range, that is, a position α is shifted to a position α′ as shown in FIG. 8, for the purpose of displaying the current vehicle position without a de-railing of the position away from the road.
However, the above matching control causes a problem when the vehicle enters a facility as described in the following. That is, as shown in FIG. 9, when the vehicle makes a left turn for, for example, entering a facility such as a gas station or the like at the intersection, the current vehicle position is matched to a matching link within the tolerance range after a search of the matching link triggered by a start and an end of the turn of the vehicle based on a travel locus of the vehicle on a link that corresponds to the current vehicle position. That is, a position β is shifted to a position β′ as shown in FIG. 9. In that case, the vehicle is falsely determined as making a left turn at the intersection when the vehicle is actually turning for entering the facility, and a subsequent processing is performed with reference to a position immediately after the matching control, thereby leading to a de-railing of the display of the current vehicle position away from a link when the vehicle exits from the facility.
The false determination and the problem may be resolved when a white line painted on the road is detected for the determination whether or not the vehicle has entered the facility as disclosed in the above Japanese patent document. However, the method in the above disclosure requires an imaging device for capturing an image in the traveling direction of the vehicle as well as a function for analyzing the captured image for detecting the white line in the image. That is, the problem cannot be solved without increasing the costs.